This is a 2-part, multi-center, randomized, double-blind, placebo-controlled, multiple dose escalation study, enrolling approximately 48 subjects. Part A of the study will enroll subjects with Systemic Lupus Erythematosus (SLE) without Glomerulonephritis (GN) into 3 cohorts. Part B of the study will enroll SLE subjects with GN into 3 cohorts. The purpose of the study is to evaluate the multiple dose of AMG 811 on safety. Tolerability and pharmacokinetics.

Part A of the study will enroll SLE without GN (non-renal) subjects into 3 cohorts (6 AMG 811: 2 placebo). All subjects will receive a dose of AMG 811 or placebo every 4 weeks beginning with Day 1 (D1) for a total of 3 injections. Subjects will be followed through to study day 197, 5 months from the last dose of study medication.

Part B of the study will enroll SLE subjects with GN into Cohorts 4, 5, and 6 (6 AMG 811: 2 placebo). Similar to Part A, subjects in Cohorts 4, 5, and 6 will be dosed every 4 weeks with AMG 811 or placebo for a total of 3 injections followed by a 5 month follow-up period. For Cohort 6, subjects will be followed by a 6 month follow-up period.

Inclusion Criteria:

• Men and women, between the ages of 18 and 70 years of age;
• Body mass index from 18 to 40 kg/m2 [Body Weight (kg)/Height2 (m2)] at screening;
• Diagnosis of SLE at least 6 months before randomization, including a positive antinuclear antibodies (ANA) during screening; if screening ANA is negative, documented historical ANA with a titer of at least 1:80 will be acceptable;
• Any concurrent SLE pharmacologic regimen (including mycophenolate mofetil, azathioprine, leflunomide, methotrexate, and anti-malarials) must be stable for at least 30 days before randomization;
• Prednisone ≤ 20 mg/day (or equivalent) is permitted; one increase or one decrease of ≤ 5 mg/day prednisone equivalent will be allowed within 30 days before randomization;

Additional inclusion criteria for Part B:

- Active SLE with GN with no other apparent cause, defined by the following: Renal biopsy evidence (within 18 months) of nephritis using the WHO or International Society of Nephrology (ISN)/Renal Pathology Society (RPS) classification of SLE with GN (Class III or IV); Urine protein/creatinine ratio (UP/Cr) > 1 or 24 hour urine protein > 1g after at least 12 weeks of treatment with mycophenolate mofetil (at least 1.5 grams/day) or azathioprine (at least 100 mg orally per day); Superimposed membranous changes are allowed for those with Class III or Class IV SLE with GN;

- Prednisone ≤ 20 mg/day (or equivalent) at the time of randomization.

Exclusion Criteria:

• Any disorder (including psychiatric), condition or clinically significant disease (other than a diagnosis of SLE) that would, by its progressive nature and/or severity, interfere with the study evaluation, completion and/or procedures per the investigator's discretion;
• Creatinine clearance within the screening period of less than 50 mL/min as calculated by the Cockcroft-Gault method
• Signs or symptoms of a viral, bacterial or fungal infection within 30 days of study randomization, or recent history of repeated infections;
• Underlying condition other than SLE or being on allowed immunosuppressants that predisposes one to infections
• Prior use of the following agents:
• Administration of an investigational biologic agent that primarily targets the immune system
• Administration of cyclosporine, tacrolimus, sirolimus, IV immunoglobulin, and/or plasmapheresis within 3 months of randomization;
• Administration of oral or IV cyclophosphamide (or any other alkylating agent) within 12 months (Part A) or 3 months (Part B) of randomization;
• History of ethanol or drug abuse within the last one year prior to randomization;

Additional exclusion criteria for Part B:

• Rapidly progressive GN (defined as a doubling of serum creatinine within the past 3 months);
• Evidence of significant chronicity, defined as:

> 50% glomeruli with sclerosis or > 50% interstitial fibrosis on renal biopsy; or International Society of Nephrology (ISN)/Renal Pathology Society (RPS) 2003 Class III (C), IV-S (C) or IV-G (C).